dotty the chasing and mounting is pretty normal boar behaviour, especially as yours are going into the Terrible Teens.
Give them lots of distraction and escape places. Boxes with two doors cut in them so that one boar can't trap the other.
And as you've seen it's not always the larger boar that's the villain.
Our first GP fight was the result of a coriander binge and it was my GP2 that started it.
A month or so ago, GP1 was following and headbutting GP2, pushing his head over GP2 back and going for his ears but there was no biting involved, just noise and bluster.
GP2 didn't respond, he took himself off to another housie and muttered darkly.
There are websites that will give you the GP signs (if you Google boar aggression) but
rumblestrutting (stiff body, continual purrrrrrr, sometimes jumping and turning 180 degrees, waggling bum)
headbutting
pushing each other out of the way
heads up - higher and higher until one gives up
quiet chattering
Is low level
loud chattering
lungeing
front legs leaving the ground
is keep a check on and prepare to distract
rearing up
proper lunging
getting their teeth into each other (they can go for throat, back)
is get in there with a towel , wear garden gloves, they can bite.
Hopefully they won't get to that level.
Mine had to be seperated at night in Winter 2011 after their fight (they don't like their indoor cage) but we always made sure they were together in the day.More room in the day house.
Lots of food to distract. Big hay piles to burrow in.
I have no idea what mine get up to by day but I know GP1 protects GP2 in the run.He watches while GP2 sleeps. He checks out the cage first.
But he expects to be first to the food. And if they both remember there place, all is fine.
Though finding the Boar Glue (yes it is that ) is a worry.Mine are brothers 